The exemplary embodiment described herein is related to the field of electrophotographic image reproduction and, more particularly, relates to the protection and confirmation of hard copies of image data.
The introduction of the plain paper copier has resulted in a proliferation of paper copies of paper originals. A similar result is happening to electronic images, given the easy availability of scanners and a quick and widespread access to images throughout the Internet. It is now very difficult for the creator of an image to generate an electronic original, for which he can be assured that illegal copies will not be spread to third parties. It is no wonder that the copying of confidential documents is a concern to business owners and the like. Unauthorized copying and distribution of confidential customer data, financial records, employee information, product specifications and other sensitive documents can lead to disaster. Leaks of confidential information can result in lost revenue, compromised ability to compete, unfairness in purchasing and hiring decisions, diminished customer confidence and more. For instance, if a company's payroll report gets circulated, it could end up with disgruntled employees. Accordingly, attempts to protect the hardcopy have been devised, including watermarks and security paper.
In a paper document, a watermark is a physical design embossed or pressed into the paper that can be seen when the page is held up to a light. In an electronic document, watermarks come in two forms: visible and invisible. A visible watermark is usually a faint background image superimposed on the document image, but if well done, it will appear to be “under” the image, as if the image on the screen were an image of an original printed on watermarked paper. Invisible watermarks are often not images at all but patternless arrangements of bits hidden in an image or sound file which are recovered from the file through a decoding application. For example, U.S. Pat. No. 5,734,752 to Knox, entitled “Digital Watermarking Using Stochastic Screen Patterns” and incorporated by reference herein, discloses a method for generating watermarks in a digitally reproducible document that are substantially invisible when viewed.
One function of a visible digital watermark is to make it apparent to a user that a document is owned and by whom. A visible watermark itself is typically a fairly complex design to make forgery difficult. Unfortunately, the technology for imprinting watermarks into digital images can be readily obtained, and as programs can be written to accurately recover a watermark from a digital image, digital forgery can be accomplished by any skilled person using a desktop computer. By specially designing the graphic used as a watermark, electronic watermarks can be created which are only visible when an image is printed, and do not appear on screen images. Such techniques were developed to block counterfeiting of financial documents using photocopiers or laser printers, and depends on particular features of the way today's copiers and printers are constructed. Likewise, invisible watermarks are also intended to record the legal source of a document, (which may be the copyright owner), but in such a way to be undetectable by the user.
Security paper may also be used to help prevent the unauthorized duplication of a printed document. Security paper is paper that has been “engineered and manufactured” and incorporates physical features imbedded into the paper itself to resist the document forgery and the copying of negotiable documents when these documents are printed on MICR Laser printers. The paper is fully compliant with the physical paper standards of weight, grain direction, moisture content etc. for MICR Laser printers but has additional “chemical and fiber fraud resistant features” built into the paper during the manufacturing process. Plain laser printer paper meets the physical standards of the Laser printer but does not possess any of the capabilities of fiber, chemical, or external processes that make “security paper” fraud resistant and tamper proof. Security paper provides assistance to a financial institutions “back office processing” of checks by making check fraud tampering attempts physically obvious to the institutions check review personnel and prompts the reviewer to look at the document more closely for any form of tampering prior to the check being cleared for payment by the institution. The features themselves cannot be readily copied or reproduced via conventional reproduction processes. Security papers are used, for example, in stopping forged checks from being cleared and paid against business accounts. However, a document that contains a security feature such as a “VOID” background may be easily duplicated on some photo copiers without the word VOID showing up on the copy.
In view of the foregoing issues, there is a need for a more secure method for protecting and confirming printed documents.